Ramsey QRP40 User Manual

40 METER (7MHz) CW TRANSMITTER

Ramsey Electronics Model No. QRP40

THE RAMSEY QRP-40 IS AN AMAZING PERFORMER THAT WILL WORK THE WORLD ON ABOUT A WATT! FOLKS OF ALL AGES HAVE SUCCESSFULLY BUILT AND ENJOYED THIS EASY, FUN KIT.

• Ideal for portable or travel fun

• VCXO design allows up to 5 KHz of tuning about the crystal

frequency

• Front panel switching of TWO channels and includes a crystal for

7.040 MHz, the International QRP frequency

• Excellent and clean keying waveform

• Built-in antenna T-R switch

• Operates on 12 - 15 volts DC at 1/4 amp current

• Appoximately 1 Watt RF power

• Clear, concise step-by-step instructions carefully guide you to a

finished kit that not only works - but you’ll also learn too!

• Proven design that has won many of awards for operators around

the country!

• Add our case and knob set for a finished ‘Pro’ look. Cases match all

Ramsey products

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PARTIAL LIST OF AVAILABLE KITS

RAMSEY TRANSMITTER KITS

• FM10A FM Stereo Transmitter

• FM100B Professional FM Stereo Transmitter

• FM25B Synthesized FM Stereo Transmitter

• AM25 Synthesized AM Transmitter

• AM1 AM Transmitter

RAMSEY RECEIVER KITS

• FR1 FM Broadcast Receiver

• AR1 Aircraft Band Receiver

• AA7 Active Antenna

• SC1 Shortwave Converter

• SR2 Shortwave Receiver

RAMSEY HOBBY KITS

• SG7 Personal Speed Radar

• SS70 Speech Scrambler

• TT1 Telephone Recorder

• SP1 Speakerphone

• MD3 Microwave Motion Detector

• PH10 Peak hold Meter

• TFM3 Tri-Field Meter

RAMSEY AMATEUR RADIO KITS

• DDF1 Doppler Direction Finder

• HR Series HF All Mode Receivers

• QRP Series HF CW Transmitters

• CW7 CW Keyer

• CPO3 Code Practice Oscillator

• QRP Power Amplifiers

RAMSEY MINI-KITS Many other kits are available for hobby, school, scouts and just plain FUN. New

kits are always under development. Write or call for our free Ramsey catalog.

40 METER CW TRANSMITTER KIT INSTRUCTION MANUAL

Ramsey Electronics publication No. QRP40 Revision 1.3

First printing: January 1995

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Ramsey Publication No. QRP40

Price $5.00

KIT ASSEMBLY

AND INSTRUCTION MANUAL FOR

QRP40 40 METER CW TRANSMITTER KIT

TABLE OF CONTENTS

Introduction to the QRP40 ............. 4

Understanding Power Levels ......... 5

Circuit Description .......................... 7

Simplified Block Diagram ............... 8

Parts List ........................................ 9

Schematic Diagram ...................... 10

Parts Layout Diagram .................. 11

Assembly Instructions .................. 12

Crystal Oscillator Testing ............. 16

Initial Tests ................................... 17

Verifying RF Power ...................... 18

Maximizing RF Power Output ...... 19

Options for Finishing Project ........ 20

Enclosure Ideas ........................... 20

Choosing Crystals ........................ 20

Troubleshooting Guide ................. 21

Ramsey Kit Warranty ................... 22

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RAMSEY ELECTRONICS, INC.

590 Fishers Station Drive

Victor, New York 14564

Phone (585) 924-4560

Fax (585) 924-4555

www.ramseykits.com

INTRODUCTION:

Most "QRP" transmitters are one-of-a-kind experimental circuits which take some patience and fine-tuning to get clean keying and satisfactory performance. Most QRP building projects presume either unlimited radio junkboxes with all the right coils and capacitors, or that you have a lot of time on your hands to track down needed parts. And that is part of what ham radio can be all about. The purpose of the Ramsey Electronics series of QRP transmitters is to give our amateur radio customers the option of picking up a truly complete and reliable transmitter kit for whenever you need a compact CW rig for a particular opportunity, perhaps a camping or business trip or a weekend contest, or something economical to share with a favorite new Novice.

This transmitter is a serious and practical device for radio amateurs with general interests, as well as for QRP enthusiasts.

NOTE TO NEWCOMERS: "QRP" is amateur radio shorthand referring to operation at "reduced power". As a standard "Q-signal", the CW expression "QRP?" really means all of this: "If you are receiving me so well, and since the FCC requires that we use minimum power necessary to maintain useful communication, do you think I should reduce transmitting power?" The act of reducing power output can be the switching off of a linear power amplifier, or switching from 25 to 5 watts on your new Radio Shack 10 meter rig or turning back the carrier level control on most modern transceivers. For equipment description and contest competition purposes, "QRP" refers to transmitter powers under 5 watts.

In our manuals for the Ramsey Amateur Band receivers for the 80 and 40 meter bands, which tend to be of interest to many beginners because of available Novice and Technician operating privileges, we try to be very basic and patient, hoping that such an approach will be helpful to radio newcomers as well as to casual, licensed amateurs who just did not know that worthwhile radio gear could be constructed at Ramsey's low prices, even in the 1990's.

Talking through a transmitter project presents a different challenge. Talking through a multi-stage transmitter that delivers a grand total of one or two watts to your antenna is an even greater challenge. In these times when a "barefoot rig" is assumed to be an imported, digitally-synthesized transceiver putting out over 100 watts at a cost of $1000-2000.00, we need a sensible and helpful way of talking about this QRP transmitter you are about to construct.

It's easy to prove that Ramsey's popular and economical receivers work just fine. Build one right, turn it on, and we become easily convinced. A transmitter is a different story, especially a transmitter that runs low QRP power! Different from a receiver, you want to see some measurable output power and you especially want to make two-way contacts!

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If you're studying this manual before deciding to try this Ramsey "QRP" transmitter project, perhaps the following discussion will be helpful to you. The purpose of this manual is to help you construct this Ramsey Electronics 4stage, variable-frequency CW transmitter efficiently and successfully, not necessarily to "sell" you on the merits and fun that have been discovered in ham QRP operation. The purpose of the following discussion of power levels and signal reports is simply to assure you that your new Ramsey QRP transmitter is capable of serious, long-distance communication.

1000 WATTS vs 1 WATT: UNDERSTANDING THE DIFFERENCE

Before we move on, I would like to share with you a practical formula about transmitter power that I clung to in my younger years when I could not afford anything other than my original Novice CW transmitter, even well after I got my Extra Class license. First, some theoretical facts we should know:

• 1. An "S-unit" on a receiver's S-meter or in the R-S-T system consists of a

6 - decibel increase or decrease of output power received from a transmitter.

• 2. Power needs to be increased four times or 400% to result in a true 1 S-

unit or 6db RST gain.

• 3. Reducing output power down to 25% of previous power should result in

an S- Meter or RST drop of only one 6-db unit.

• 4. A 10 - decibel increase in signal strength requires a power increase of

ten times!

Next, there are three practical facts to remember:

• 1. The R-S-T system was designed originally for the human ear and was

based on typical receiver performance of over 50 years ago.

• 2. Modern receiver design permits signals which are technically "weak" in

measured decibels to sound quite good (ie: 569-579) to the ear.

• 3. The human ear is sensitive enough to appreciate a 1 or 2 db change in

signal strength, which is why moderate changes in output power often result in more dramatic signal report changes. (In fact, the value of a decibel was determined to be that increment of sound change which the ear could detect!)

The following example shows RST reports to be expected, in exact theory, at various power reduction levels. We will start with the classic 1000 watt station which gets a report of "10 db. over S-9" measured on the receiving station's Smeter. Assume identical dipole antennas at both stations. Our chart does not start at the proverbial "30 db. over S-9" and work itself down to S-1 for reasons that will become obvious.

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S9+10 db. 1000 watts output S9 100 watts output S8 25 watts output S7 6.25 watts output S6 1.56 watts output S5 .39 watts output

We can see that it becomes easy to play games with such numbers. For example, an RST of 439 is a legitimate report which permits reasonably effective communication. But, do we believe that the transmitting station illustrated above could really produce a 439 signal by running .0013 watt? If we say "probably not", we also ask why not, and then we would get the seminars about perfect antenna matching, transmission line losses, and so forth.

Under good propagation conditions, SSB signal reports of "20 over S-9" and more can be given without even needing 1000 watts or a beam antenna. Assuming the "+20" is an accurate report, consider this example of power reduction over the same path:

S9+20db. 1000 watts S9+10db. 100 watts S9 10 watts S8 2.5 watts S7 .625 watts S6 .156 watt S5 .039 watt S4 .0087 watt!

Under reasonably good band conditions, particularly at 10 or 14 MHz and on up, the above correlation of signal reports to power output becomes realistic. "S9+20" is what amplifier users expect to give and receive to justify their investment and power consumption. Most commercial transceivers have typical output in the 60-200 watt range, and S8-9 reports are taken for granted. Actually, 15-25 watts is a far more practical operating power than most amateurs and equipment vendors realize today...and the thousands of QRP enthusiasts will confirm that getting a solid 579 running 3-4 watts is no big deal.

If all the above theoretical signal reports are based on both the transmitting and receiving stations using simple dipole antennas, we can also see that the use of some 10db gain antenna such as a beam or quad by either station could move the S7 for .625 watt up to S8, and that a similar antenna used at the other station could give the under 1 watt signal a further boost over S9!

On the other hand, if you hear a 1000 watt station producing a moderate signal such as S4 or S5, you can reasonably assume that you will not have a lot of luck over that path right now with the theoretical S1 signal level of your QRP transmitter.

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While these figures also can be used to show how nice it is to have a power amplifier and beam antenna, they indeed serve to show that reasonable signal levels indeed are achievable with low power and a dipole antenna.

"QRP" enthusiasts have their own rituals, jargon, strategies, QRP operating contests, magazine columns and books, and convention get-togethers. They constitute a vital segment of the amateur radio community, because they consistently demonstrate the feasibility of low-power communication. In fact, the most avid QRP enthusiasts would not regard communication with a Ramsey transmitter especially challenging, since they prefer the new world of milliwatt operation, known as "QRPp"! And, yes, the ones who have conquered the "milliwatt" world ARE setting records with "milliwatt" tests. With the world record set in 1970 between Alaska and Oregon on ONE microwatt, think about it this way: your Ramsey QRP transmitter is almost one million times more powerful than the transmitter used in that historic test!

WHO SHOULD USE A "QRP" TRANSMITTER?

There is a philosophy that "Novices" should not get started with a very low power transmitter. The reasoning is that most newly-licensed amateurs need to build up the confidence that comes with actually making contacts and that they do not need the additional challenge and pressure of low-power operation. There is some wisdom in this view, but that opinion should not make newcomers apprehensive about trying a Ramsey QRP transmitter, IF:

1. This is where your budget is.

2. You can count on somebody to help you with assembly.

3. You can count on somebody to listen to your signal during initial tests.

4. You have a reasonably good receiver.

5. You have space for a normal, no-compromise antenna for the band you wish to operate, either a standard dipole, or the "inverted V" dipole, or quarter-wave vertical.

CIRCUIT DESCRIPTION:

In brief, Q1 is a crystal oscillator, amplified by buffer stage Q2, which drives Q3 as the RF output amplifier. Q4 is a PNP keying circuit which opens and closes the 12VDC supply line to Q1 and the T-R circuitry of D1 and D2.

S1 selects either of two crystals. R1,D3,D4 and L1 form a varactor controlled series resonant circuit with the crystal. Adjusting R1 permits a crystal frequency swing of up to 7 KHz, about the crystal frequency.

Q3 is a Class C RF amplifier that amplifies the RF output of Q2 to the final RF power output level.

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L6,C17 and C18 form a low pass filter (Butterworth) to match the output of Q3 to the antenna and reduce harmonics to acceptable levels as specified by the FCC.

When the keying line is closed, Q4 conducts +12VDC to the oscillator stage, applies a positive bias to the base of Q2 through R8, and +12VDC through choke L4 to the anode of D1, which permits RF to pass through D1 to the filter network while applying negative bias to D2 which blocks RF from passing to the receiver. When the keying line is open, the +12VDC applied to D2 through R13 permits D2 to conduct from the antenna jack to the receiver jack. The buffer and amplifier stages are not keyed, resulting in clean keying, free of chirps and clicks.

BLOCK DIAGRAM:

OSC.

A B

Q2 BUFFER

Q3 FINAL

AMP

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D1, D2

DIODE

SWITCH

C17.L5,C18 LOW PA SS

FILTER

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